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We propose a concept of supramolecular materials for effective all-optical generation of surface relief structures and optical anisotropy. The materials are based on the ionic interactions between photochromic azobenzene units and polyelectrolytes. The materials are easy to produce and they allow the inscription of the 1.8 m deep surface relief gratings. Moreover, the induced structures were thermally very stable. Both distinctive features of the new materials, namely, the dynamic behavior of molecular orientation and the high thermal stability of surface structures, have been explained in terms of the network of oppositely charged ions inherent to the materials. Due to the simplicity and versatility of the concept, the new family of materials for different applications in optics, sensorics, and biology may be designed. [ABSTRACT FROM AUTHOR]

A photosensitive fluorescent cholesteric guest−host mixture consisting of a nematic polyacrylate, a chiral, photochromic dopant sensitive to UV light, and a fluorescent dopant was prepared. The nematic polyacrylate contains 4-phenyl-4‘-methoxybenzoate nematogenic side groups and photochromic 4-cyanoazobenzene side groups. The chiral-photochromic dopant formed by isosorbide and cinnamic acid is capable of E−Z photoisomerization and [2 + 2] photocycloaddition under light irradiation. The planarly oriented films possess a selective light reflection in the visible spectral region coinciding with the emission peak of the fluorescent dopant. The fluorescence emitted by the planarly oriented films of the mixture is strongly circularly polarized and characterized by a large value of the dissymmetry factor. At temperatures below glass transition (Tg) the polarized light action of an Ar+ laser (488 nm) leads to the photoorientation of the azobenzene fragments resulting in a strong and reversible disruption of the selective reflection and a decrease of the dissymmetry factor of fluorescence. UV irradiation leads to E−Z isomerization and/or [2 + 2] cycloaddition of the chiral-photochromic dopant, causing an irreversible shift of the maximum of the dissymmetry factor to a long-wavelength spectral region under subsequent annealing at temperatures higher than Tg. Such multifunctional glass-forming guest−host mixtures combining photosensitive and fluorescent properties with the unique optical properties of cholesteric liquid crystals can be considered as promising material for optical data processing technologies and photonic applications. [ABSTRACT FROM AUTHOR]

New nanocomposites containing functionalized acrylate monomers and Au nanoparticles (NPs, 1.5−3 nm core diameter, 1−2 wt %) have been developed for an all-optical fabrication of periodic bulk structures by holographic photopolymerization. The Au NPs were coated with ethyl 11-mercaptoundecanoate to ensure good solubility in low-polarity organic media. The materials with only 1.5 wt % Au NPs show unusually high amplitude of the refractive index modulation in the diffraction volume gratings (0.0073). Both volume and surface relief gratings are formed during the holographic exposure. The proposed mechanism of the refractive index contrast amplification (as compared to monomer mixture without NPs) includes interception of free radicals by Au nanoparticles. This slows down the free-radical photopolymerization, thus promoting the increase in lateral periodic redistribution of the components in the interference pattern. The redistribution of both NP and monomers provides high efficient grating formation with the spatial period of 0.5−4.5 μm. The formation of the surface relief coincident with the interference pattern is also observed. The introduction of 1.5 wt % Au NPs into the prepolymer mixture more than doubles the surface relief depth (from ca. 150 to 400 nm for the period 4.2 μm), thus proving the NP influence on the structure and, consequently, on the shrinkage of the polymer matrix. [ABSTRACT FROM AUTHOR]

We propose a concept of supramolecular materials for effective all-optical generation of surface relief structures. The materials are based on the ionic interactions between oppositely charged photochromic azobenzene units and polysiloxane backbones formed in situ. The materials are easy to produce from commercial components. Using ionic interactions to connect photochromic units to the polymer backbones allowed very high dye-doping levels without aggregation. Because of this noncovalent bonding the polymer chains got involved in the photoinduced translation motion of azobenzene units resulting in very effective formation of surface relief gratings. For the first time some relaxation processes which counteract the light-induced formation of surface relief structures were suggested. Under consideration of these processes the influence of network formation and alternatively of glassy state on the efficiency of mass transport and the stability of induced structures was discussed. Because of the simplicity and versatility of the concept the new family of materials for applications in optics, sensorics, and biology may be designed. [ABSTRACT FROM AUTHOR]